1. Field of the Invention
The present invention relates to a lens-fitted photo film unit, more particularly to a lens-fitted photo film unit in which, before loading and after unloading of a cassette, photo film is reliably protected from unwanted exposure to ambient light.
2. Description Related to the Prior Art
Lens-fitted photo film units (hereinafter referred to simply as film units) are now on the market, e.g. under the trade name "Fujicolor Quick Snap" (manufactured by Fuji Photo Film Co., Ltd.). Such known film units are a single-use camera pre-loaded with a photo filmstrip (hereinafter referred to as film). A user who has purchased the film unit winds the film frame by frame back into the cassette after each exposure. The film unit in its entirety is forwarded to a photo laboratory after use.
The photo film unit is pre-loaded with the conventional 135-type photo film cassette similar to what is used in a conventional camera, and includes a cassette shell which is constituted of a tube formed from a thin metal plate and a pair of end caps. The photo film is retained on a spool formed from resin. The spool is contained in the cassette shell rotatably. A film passage port is formed in the cassette shell. The photo film is drawn out of the passage port while wound as a roll. Plush or light-trapping ribbons are attached to the inside of the passage port, so as to prevent ambient light from entry into the cassette shell through the passage port.
In such a metal-shell cassette containing 135 photo film, a leading end of photo film is protruded from inside a cassette shell even before use of the photo film. To load a camera with the cassette, a user is required to handle the cassette while paying attention not only to the cassette shell but to the protruded leading end. To overcome these difficulties associated with handling the conventional photo film cassette at the time of inserting it into a camera, a cassette has been proposed in which not only a roll but a leading end of photo film is pre-contained in a cassette shell, and rotation of a spool causes the leading end to advance to the outside of the cassette shell, upon separation from the roll by a separator structure disposed in an innermost position along and inside the passage port. It is also known, to use an openable resinous light-shielding member for preventing light from entering the inside of the cassette shell through a passage port for the photo film, instead of the plush.
It is also known to construct a mechanism inside a cassette for regulating a spool in latched and unlatched positions. Should a cassette be vibrated or shook in transportation or manual handling, a roll of photo film therein will be loosened. A photosensitive surface of the photo film can thus be scratched, after turns of the photo film lying one on another, or else the photo film and a cassette shell, have contacted each other. Should the cassette be of a leader-exiting type, even rotation of the spool will fail to exit a leading end from the cassette because the position of the leading end inside the cassette will be deviated inappropriately from a desired position. In order to cope with those difficulties, the known spool-regulating mechanism latches the spool so as to stabilize the entire orientation of the photo film.
In view of use in a lens-fitted photo film unit, it is desirable to provide such a leader-exiting structure and spool-regulating mechanism for a photo film cassette. This is because it is favorable to conceive various uses of the cassette. For example, the cassette, after exposure of the photo film, could be loaded into an automatic photo film processor or an automatic photo printer while containing the exposed photo film; and after development of the photo film, the cassette could be loaded into a known photo film video player while containing the developed photo film, so as to use the photo film while drawing it out of the cassette. A "photo film video player" is an instrument for picking up an on the photo film to display a positive image of the image from the photo film on a CRT.
Any photo film cassette, after being removed from a packaging or a photo film unit, does not readily indicate the status of the photo film inside, either unexposed, exposed or developed, because the status of the photo film cannot be discerned externally. Nowadays there is a proposal that external apparatuses for use with the photo film be adapted to loading with the entirety of the photo film cassette containing the photo film. It is conceivable to load a wrong apparatus with the cassette, e.g. load a camera with a cassette containing exposed photo film, resulting in double exposure, or load the processor with a cassette containing the developed photo film. The cassette containing the photo film of any status of being unexposed, exposed and developed, therefore, requires prevention of these errors in manual handling.
U.S. Pat. No. 4,965,600, in view of such a situation, discloses a photo film cassette, and a camera for use with the same, in which a status of photo film in the cassette is indicated externally as one of being Completely Unexposed, Partly Exposed or Completely Exposed.
However, the openable passage port, having the light-shielding member as described above, might admit ambient light into the cassette shell and would subject the photo film in the cassette to light even after photography. The known cassette having the resinous shell has such a disadvantage. The exposed photo film is withdrawn from the cassette which has been unloaded from the photo film unit. Prior to unloading the cassette from the photo film unit, the light-shielding member of the cassette placed in the illuminated room must be kept closed tightly by external operation. If the exposed photo film is handled in the darkroom before withdrawal from the photo film unit, this results in low efficiency and inconsistency of processing of photo films with accumulated cassettes.
It follows that the above mentioned difficulties of the resinous cassettes make it difficult to take advantage of the idea of incorporating a leader-exiting structure in such a cassette. Should a cassette lack a leader-exiting structure, the cassette must be disassembled or broken before the photo film can be loaded into a photo film processor or printer. Thus automation in loading such devices with the photo film is unavailable, so that improvement in efficiency is limited.
The construction disclosed in U.S. Pat. No. 4,965,600 has also a problem in that the photo film unit to be used with the cassette must incorporate a complicated arrangement inclusive of a device for driving the indication for the status of the photo film, a device for driving the spool, and a double exposure preventive device for avoiding loading of the cassette which contains the exposed photo film. This is unfavorable in terms of a lack of consistency of a photo film unit. Also, the relevant devices are large in dimension and the devices expensive to manufacture.